Improve the log LogRequestHandlerCompleted to include the request duration

[Meir017]

Is your feature request related to a problem? Please describe.
The log

csharp-sdk/src/ModelContextProtocol.Core/McpSessionHandler.cs

Line 779 in e6db415

private partial void LogRequestHandlerCompleted(string endpointName, string method);

just mentions the request completed.

I think we should improve it to be more like the aspnetcore request completed log that includes the duration, maybe also content length.

called from here

csharp-sdk/src/ModelContextProtocol.Core/McpSessionHandler.cs

Lines 348 to 350 in e6db415

	LogRequestHandlerCalled(EndpointName, request.Method);
	JsonNode? result = await handler(request, cancellationToken).ConfigureAwait(false);
	LogRequestHandlerCompleted(EndpointName, request.Method);

maybe we could measure the duration here?

sample logs as seen in vscode